Chain saw guide bar

Abstract

The present disclosure relates to a guide bar ( 1 ) for a chain saw ( 3 ) with a proximal section ( 7 ), a distal section ( 13 ), and an intermediate section ( 15 ) between the proxymal and distal sections. The periphery of the guide bar defines a saw chain guide for guiding saw chain links along a path ( 31 ) from an engagement location ( 27 ) one edge of the bar to a disengagement location on the other. The periphery of the guide bar, where the saw chain links are supported only by the guide bar periphery has a curvature which is free from abrupt changes or step-wise changes. This provides a guide bar ( 1 ) less subject to wear during use.

1 . A guide bar for a chain saw, having a proximal section configured to be connected to a drive unit of the chain saw, a distal section, and an intermediate section between the proximal and distal sections, wherein a periphery of the guide bar defines a saw chain guide for guiding saw chain links along a chain path from an engagement location on one edge of the proximal section to a disengagement location on an opposite edge of the proximal section, wherein the periphery of the guide bar has a curvature defined as the shortest distance, x, between a central reference point on the periphery, and a virtual straight line between a first lateral reference point and a second lateral reference point on the periphery, wherein the first and second lateral reference points are located at either side of the central reference point at a 1 mm distance the to the central reference point, wherein the curvature x has a local rate of change Δx/ΔL being less than 0.01 mm for an ΔL=2 mm displacement at each position along said chain path where the saw chain links are supported only by the guide bar periphery. 
     
     
         2 . The guide bar according to  claim 1 , wherein the guide bar comprises a sprocket guiding the saw chain in a part of the distal section. 
     
     
         3 . The guide bar according to  claim 2 , wherein the saw chain links are supported by the sprocket in a sector ranging from 105-180° at the distal section. 
     
     
         4 . The guide bar according to  claim 1 , wherein the guide bar is formed by a plurality of layers which form a groove along the guide bar periphery. 
     
     
         5 . The guide bar according to  claim 4 , wherein the groove has a uniform depth along said chain path outside the proximal section. 
     
     
         6 . The guide bar according to  claim 1 , wherein the periphery of the intermediate section has a positive curvature on both edges of the guide bar. 
     
     
         7 . A guide bar for a chain saw, having a proximal section configured to be connected to a drive unit of the chain saw, a distal section, and an intermediate section between the proximal and distal sections, wherein a periphery of the guide bar defines a saw chain guide for guiding saw chain links along a chain path from an engagement location on one edge of the proximal section via the distal section, to a disengagement location on an opposite edge of the proximal section, wherein the periphery of the guide bar has a curvature defined as the shortest distance between a central reference point on the periphery, and a virtual straight line between a first lateral reference point and a second lateral reference point on the periphery, wherein the first and second lateral reference points are located at either side of the central reference point at a 1 mm distance the to the central reference point, wherein the curvature has a positive rate of change in a first portion of the proximal section and a negative rate of change in a second portion of the proximal section in a direction towards the distal section.